Forging machine



Jan. 12, 1965 KRALOWETZ 3,165,012

FORGING MACHINE Filed Nov. 16, 1962 4 Sheets-Sheet 1 FIG. '1 1 T Jan. 12, 1965 Filed Nov. 16. 1962 4 Sheets-Sheet 2 MIME/179E B. KRALOWETZ FORGING MACHINE Jan. 12, 1965 4 Sheets-Sheet 3 Filed Nov. 16. '1962 an I Jan. 12, 1965 B. KRALOWETZ 3,165,012

. FORGING MACHINE Filed Nov. 16, 1962 4 Sheets-Sheet 4 //VUEl/TOZ United States Patent 3,165,012 FORGING MAQHINE Bruno Kralowetz, St. Ulrich, near Steyr, Austria Filed Nov. 16, 18962, Ser. No. 238,099 Claims priority, application Austria, Dec. 21, 1961, A 9,670/61 9 Claims. (Cl. 78-22) This invention relates to a forging machine having preferably four hammers which are radially directed towards the axis of the workpiece and are driven by eccentries and have driving shafts eccentrically mounted in cylindrical housings rotatably adjustably mounted in the forging box. Whereas the eccentric shafts cause the hammers to perform a reciprocating working movement, the rotary adjustability of the housings of these driving shafts serves for changing the stroke position of the hammers, i.e., for setting the penetration of the dies carried by the hammers so as to provide for various desired crosssectional dimensions of the workpiece. Such machines have proved satisfactory in many cases owing to their high blowing rate and the resulting short times required for working, as well as owing to the high accuracy of the forging work perform by them. On the other hand, certain difficulties are involved in protecting the machines from overload and breakage. For overload protection, shear plates disposed in the divided hammers have been used, for devices which interrupt the drive of the machine in response to the excessive current which flows under overload conidtions. If the shear plates are dimensioned in accordance with the alternating stresses which are due to the high blowing rate (number of blows per unit of time), their breaking strength will be too high for a single occurrence of overload so that they do not afford an adequate protection. The devices responsive to excessive current have the disadvantage that their response is too late because it does not occur until the reactions resulting in the machine from an overload have caused an excessive current to flow. This disadvantage has previously been taken into account by dimensioning all important elements of the machine with a high safety factor so that they were overdimensioned and capable of resisting an overload which was the result of a mistake in operation (insuflicient workpiece temperature or excessive reduction in cross-section in one forging pass). Such design features are obviously unsatisfactory and, above all, they cannot be employed when it is desired to design a machine inherently for a higher power or high forging forces because in that case the various parts of the machine and the machine as a whole would assume intolerably large dimensions.

In cases where high forging forces must be applied, e.g., to forge down ingots of high alloy steels, high-speed hydraulic presses have previously been employed, the hydraulic drive system of which affords inherently the best protection against overload by the action of overpressure relief valves. Compared to the described forging machine, however, these high-speed forging presses have the important disadvantage that their blowing rate is insufficient owing to the manipulator. This results in an insufficient forging speed and may involve a destruction of the core portion of the workpiece because only one hammer is used which acts against an anvil whereas the workpiece is rotated by increments of 90 between successive blows; on the other hand, a forging machine comprises four hammers which are evenly spaced around the periphery of the workpiece and blow at the same time.

It is an object of the invention to eliminate all these disadvantages and to provide a forging machine which has a favorable overload protection device while retaining its previous advantages so that the machine can be 3,165,012 Patented Jan. 12, 155265 "ice designed for high powers without assuming intolerably large dimensions.

The forging machine according to the invention, which is now suitable for forging down, e.g., ingots of high alloy materials, is essentially characterized in that each adjusting housing is connected to a backing piston, which is displaceable in a cylinder and under the action of hydraulic pressure, which piston retains the housing against a rotation in the hammer-opening sense during the hammer blow until a forging pressure has been reached which is determined by a suitably adjustable overpressure relief valve incorporated in the hydraulic system. Whereas the adjusting housings were previously mounted in a self-locking arrangement in the forging box, possibly with increased friction surface areas and under additional pressure applied, so that the reaction forces due to the forging forces applied during the hammer blow were unable to cause an undesired rotation of the adjusting housings, the latter are now supported by the backing piston on a hydraulic cushion. If the forging pressure becomes excessive by any mistake in operation, e.g., the introduction of a workpiece which is too cold or an excessively high reduction of the cross-section of the workpiece in a single pass, the pressure in the hydraulic system will rise and a response of the overpressure relief valve will permit of an escape of liquid so that the adjusting housings are rotated by the forging pressure in the hammer-opening sense and detrimental reactions on the ma chine and its parts are prevented. For this reason, the machine need only be dimensioned in view of the predetermined forces and the machine elements, which are designed in any case for a high power, need not be given still larger dimensions with a view to a possible overload. Besides, it is not necessary to take up the entire forging pressure at the backing piston because the piston may engage the outside periphery of the adjusting housing by means of a connecting rod or the like so that a favorable transmission ratio is obtained which is due to the eccentricity of the mounting of the driving shaft in the adjusting housing, on the one hand, and the radial spacing of the point of engagement of the connecting rod or the like leading to the piston, on the other hand.

It might be contemplated to use the backing piston with its hydraulic system only for overload protection and to use other means for rotating the adjusting housing so as to change the stroke position of the hammers and consequently the cross-sectional dimensions of the workpiece. It is more desirable, however, to apply hydraulic pressure to both ends of the backing piston and to use the same also for an arbitrary rotation of the adjusting housing; in this case, the hydraulic conduit provided with the overpressure relief valve and leading to the backing end incorporates in a manner known per se a rotaryactuated valve means, which rotates in synchronism with the driving eccentric shafts and closes the conduit during each hammer blow. At the same time of the hammer blow, which is the only time when an overload may occur, this rotary-actuated valve means provides for the formation of a backing hydraulic cushion in a closed space, which is connected only by the overpressure relief valve to the discharge conduit, whereas the backing piston can be displaced as desired between the blows so that the adjusting housing can be adjusted in one direction or the other as desired to cause the hammers to move toward each other, in order to reduce the cross-section of the workpiece, or apart from each other, in order to increase the cross-section of the workpiece.

The backing end of the backing piston is permanently supplied with liquid under pressure and has preferably a relatively smaller effective piston area whereas the other end having a relatively larger effective piston area is adapted to be selectively connected to the discharge conduit or to the pressure fluid source. In this case it is sufii cient to control the application of pressure to the end having the larger effective piston area in order to cause the backing piston to move in both directions.

Whereas the previous forging machines comprise also such a hydraulic piston drive for rotating the adjusting housings, the adjusting housings of the driving shafts of all hammers are mechanically coupled and only a one, common piston drive is provided, which does not perform a backing function.

The conduit leading to the piston end having the larger effective piston area incorporates a constant-pressure valve has connected to it between the constant-pressure valve and the cylinder a feeler-operated slide valve, which is controlled by an adjustable cam or the like and controls the discharge. The cam or the like is displaceably mounted and provided with a return mechanism, known per se, which consists of a double-armed lever, one arm of which is articulated to the cam whereas the pivot of the lever is arbitrarily adjustable and the other arm of the lever is linked by a push rod to the adjusting housing. To change the stroke position of the hammer, the pivot of the double-armed lever is displaced first to cause a displacement of the cam or the like and consequently a displacement of the feeler-operated slide valve so that the supply of pressure to that end of the backing piston which has a larger effective piston area is changed and the piston is moved in one direction or the other to cause a rotation of the adjusting housing. By the rotation of the adjusting housing, the double-armed lever is pivotally moved by means of the push rod, and the cam or the like is returned until the feeler-operated slide valve assumes an intermediate position and the hydraulic forces on both ends of the backing piston balance each other.

To enable a simultaneous and uniform rotation of the adjusting housings of all four hammers (during the forg ing of square or circular workpieces), or of pairs of diametrically opposed hammers (during the forging of rectangular workpieces), the associated devices for adjusting the cams or the like or for adjusting the pivots of the double-armed levers are provided with synchronized individual motors or are mechanically coupled.

In the previous forging machines of the kind to which the invention relates, the hammers consist of connecting rods and to permit of the oscillating movement of connecting rods are mounted in radial guides of a disc, which performs an oscillating angular motion about the workpiece axis to the extent of the connecting rod motion. This requires the connecting rod-like hammers to perform always equal and simultaneous movements. This requirement is not entirely met in the machine according to the invention providing for an individual control of the adjusting housings. Besides, in a high power machine, the guiding disc would have to be very large and its mounting would involve difliculties. To eliminate this drawback, it is a development of the invention to mount the hammers in fixed radial guides in the forging box and to provide them with a cross slide rotary joint having a slide block which embraces the eccentric and is displaceable transversely to the axis of the hammer. The slide block is cylindrical and displaceable in two appropriately shaped shell members, which are held in the hammer with central pins so as to be capable of a limited pivotal movement about the hammer axis. This arrangement will compensate inaccuracies during the manufacture and/ or assembly and will avoid clamping or canting.

An illustrative embodiment of the invention is shown on the accompanying drawing.

FIG. 1 is a sectional view taken on line 1-1 of FIG. 2 and shows the forging and transmission box with one hammer and its drive means.

FIG. 2 is an end view showing the forging machine on a smaller scale, the lower left-hand quarter being cut open on line II'II' of FIG. 1.

FIG. 3 is a side elevation showing the forging machine and FIG. 4 is a circuit diagram of the hydraulic system for rotating an adjusting housing.

Four hammers 2 evenly spaced around the workpiece 3, which is centrally guided through the forging box 1, are slidably mounted in the forging box in fixed guides 4, 5 so as to be radially reciprocable with respect to the workpiece axis. The hammers 2 are driven by eccentrics 7 carried by shafts 6. The hammers are connected to the eccentrics 7 by cross slide rotary joints. The eccentrics 7 are embraced by a cylindrical sliding block 8, which is slidable transversely to the hammer shaft in appropriately shaped shell members. The shell members 9 have central pins 10 mounted in the hammer 2 for a limited pivotal movement about the hammer axis. A rotation of the driving shafts 6 will reciprocate the hammers 2 in the radial direction of the workpiece while the sliding blocks 8 perform a transverse movement in the cross slide rotary joint.

The driving shafts 6 are eccentrically mounted in cylindrical housings, which are capable of rotary adjustment in the forging box 1. Owing to this eccentricity, a rotation of the adjusting housings 11 will change the distance from the driving shafts 6 to the workpiece axis. This enables an arbitrary adjustment of the stroke position of the hammers 2 and the penetration of the dies 12, secured to the hammers, into the workpiece.

The eccentric shafts 6 of all four hammers are driven by a common motor 13 by means of a belt drive 14 and idler gears 15 in mesh with spur gears 16 secured to one shaft 6 each (see also FIG. 4). Owing to the change of the position of the shafts 6 by the rotation of the adjusting housings 11, the spur gears 16 cannot be rigidly coupled to the shafts 6. Each spur gear 16 and a flywheel 17 carried on the shaft 6 are designed to form the two coupling discs of a cross-keyed coupling (Oldhams coupling), the cross-keyed disc 18 of which has grooves on both sides whereas the spur gear and the flywheel carry the sliding blocks 19, 20 engaging the grooves.

Each adjusting housing 11 is connected by a connecting rod 21 to a backing piston 23 slidable in a cylinder 22, which is flanged to the side of the forging box 1. In FIG. 4, a pump 24 driven by a motor 25 permanently supplies pressure oil through conduit 26 to the left-hand end of the backing piston 23, i.e., to the end having the smaller effective piston area. This conduit 26 incorporates a rotary-actuated valve means 27, which is driven by means of a geared transmission 28 from one of the spur gears 16 to rotate in synchronism with the driving eccentric shafts 6. The valve 27 is designed to shut ofl? the conduit 26 during each hammer blow, As a result, a hydraulic cushion is tightly enclosed during each hammer blow in the hydraulic system communicating with the left-hand end of the backing piston 23. An excessive forging pres sure would cause a counterclockwise rotation of the adjusting housing 11 (radially outward movement of the hammer 2) resulting in a displacement of the backing piston 23 to the left. Because the valve 27 blocks the conduit 26, the oil can escape from the left-hand piston end only through an adjustable overpressure relief valve 29, which opens to permit of a discharge of oil in response to a certain rise in pressure. This affords a very simple overload protection.

The backing piston 23 serves at the same time for an arbitrary rotation of the adjusting housing 11. From the pump 24, another conduit 31 incorporating a constantpressure valve 3!] leads to the right-hand end of the backing piston 23, i.e., to the end having the larger effective piston area. The conduit 31 has connected to it by the branch conduit 32 a feeler-operated slide valve 33, which is controlled by a displaceable cam 34 and opens a discharge conduit 44 from time to time. A displacement of the cam 34 to the right in FIG. 4, whereby the feeler-operated slide valve is urged upwardly, will result in an increase of pressure in conduit 31 because the discharge conduit 44 is blocked. Because the larger effective area is provided at that end of the cylinder where the conduit 31 opens into the cylinder 22, the backing piston 23 is displaced to the left in spite of the permanent application of pressure to the other end and the adjusting housing 11 is rotated in the counterclockwise sense to move the hammer 2 radially outwardly. Conversely, an adjustment of the cam 34- to the left will result. in a lowering of the feeler-operated slide valve 33, i.e., an opening of the discharge conduit 44, so that the oil at the right-hand end of the backing piston can flow ofi under the pressure acting on the other end. As a result, the piston 23 will move to the right and the adjusting housing 11 will be rotated in a clockwise sense (movement of the hammer closer to the workpiece).

The displacement of the cam 34 is effected with the aid of a linkage which serves also for returning the cam when the adjusting housing has been rotated. The cam 34 has pivoted to it one arm 35 of a double-armed lever 35, 36, the pivot 37 of which is arbitrarily adjustable and the other lever arm 36 of which is linked by a push rod 38 to the adjusting housing 11. The pivot 37 is provided at one end of a screw 39, the nut 40 of which is axially held in position and is rotated by a motor 42 by means of a worm gearing 41. During an adjustment of the screw 39, the point of engagement of the push rod 38 will initially form a temporary fulcrum for the lever 35, 36 so that the cam 34 is displaced in one direction or the other to adjust the feeler-operated slide valve 33, whereby the discharge conduit 44 is opened or closed and the backing piston 23 is displaced in one direction or the other. The resulting rotation of the adjusting housing 11 will now effect by means of the push rod 38 a pivotal movement of the lever 35, 36 about its pivot 37 so that the cam 34 is returned until the feeler-operated slide valve 33 has assumed an intermediate position and the hydraulic forces acting on both ends of the backing piston 23 balance each other.

The motors 42 for all four hammers or for pairs of diametrically opposed hammers operate in synchronism in order to provide for a simultaneous and equal adjust ment. Alternatively, a mechanical coupling between the worm gearings 41 may be provided for. The overpressure relief valve 45 serves only for the protection of the pump 24.

What I claim is:

1. A forging machine which comprises a forging box adapted to have a workpiece passed therethrough in the direction of a longitudinal axis of said workpiece, a plurality of hammers evenly spaced around said workpiece and mounted in said housing for a movement in a radial direction with respect to said workpiece, a plurality of cylindrical housings rotatably adjustably mounted in said housings, a plurality of driving shafts, each of which is eccentrically mounted in one of said housings and carries an eccentric in driving connection with one of said hammers to move it radially inwardly with respect to said workpiece, whereby a rotation of each of said housings in one direction will cause a radially outward setting movement and a rotation in the opposite direction will cause a radially inward setting movement of one of said hammers, said machine further comprising a plurality of hydraulic cylinders, each of which contains a backing piston slidable in said cylinder and connected to one of said adjusting housings, conduit means, a source of hydraulic pressure connected by said conduit means to said hydraulic cylinders to oppose a movement of said piston in a direction corresponding to a rotation of said housing in said one direction, and overpressure relief valve means connected to said hydraulic cylinders and arranged to open and relieve pressure from said cylinders in a response to a pressure in said conduit means exceeding a predetermined value.

2. A forging machine as set forth in claim 1, which comprises four of said hammers.

3. A forging machine as set forth in claim 1, in which said conduit means and said overpressure relief valve means are connected to each of said cylinders at one end of the piston therein and which comprises further conduit means connected to and adapted to apply hydraulic pressure to each of said cylinders at the other end of the piston therein, said first-mentioned conduit means incorporating rotary-actuated valve means, said machine further comprising means for operating said rotary-actuated valve means in synchronism with said driving shafts so as to cause said rotary-actuated valve means to close said first-mentioned conduit means during each phase of the rotation of said driving shafts which corresponds to a radially inwardly directed movement of said hammers and to open said first mentioned conduit means during other phases of the rotation of said driving shafts, and means operatively connecting said pistons to said adjusting housings and arranged to transform a translatory movement of said pistons in said cylinders into an angular movement of said housings.

4. A forging machine as set forth in claim 3, in which said pistons are connected to eccentric points of said housings.

5. A forging machine as set forth in claim 3, in which each of said pistons has a relatively smaller piston area at said one end and a relatively larger piston area at said other end which comprises connecting means for connecting said further conduit means to said source of hydraulic pressure, a discharge conduit, and discharge valve means for selectively connecting said further conduit means to said discharge conduit.

6. A forging machine as set forth in claim 5, in which said connecting means comprise constant-pressure valve means and said discharge valve means comprise slide valve means, said machine further comprising a movable cam and a cam follower connected to said slide valve means and arranged to adjust the same in response to a movement of said cam.

7. A forging machine as set forth in claim 6, in which said cam is displaceably arranged and which comprises returning means for returning said cam to an initial position, said returning means comprising a push rod and a double-armed lever having one arm pivoted to said cam, another arm linked by said push rod to one of said adjusting housings, and a displaceable pivot between said arms.

8. A forging machine as set forth in claim 1, in which said forging box is provided with fixed radial guides, in which said hammers are mounted, and said hammers comprise cross slide rotary joints having a sliding block which is displaceable transversely to the axis of the hammers and embraces said eccentric.

9. A forging machine as set forth in claim 8, in which said sliding block is cylindrical and said joint comprises two shell'members conforming to and in slidable engagement with the periphery. of said sliding block and having central pins mounting said shell members in said hammers for a limited pivotal movement about the hammer axis.

References Cited by the Examiner UNITED STATES PATENTS 2,793,548 5/57 Kralowetz 78-20 2,903,923 9/59 Kralowetz 7 820 3,028,775 4/62 Kralowetz 7821 3,098,402 7/ 63 Kralowetz 7822 FOREIGN PATENTS 216,305 7/61 Austria.

WILLIAM J. STEPHENSON, Primary Examiner. 

1. A FORGING MACHINE WHICH COMPRISES A FORGING BOX ADAPTED TO HAVE A WORKPIECE PASSED THERETHROUGH IN THE DIRECTION OF A LONGITUDINAL AXIS OF SAID WORKPIECE, A PLURALITY OF HAMMERS EVENLY SPACED AROUND SAID WORKPIECE AND MOUNTED IN SAID HOUSING FOR A MOVEMENT IN A RADIAL DIRECTION WITH RESPECT TO SAID WORKPIECE, A PLURALITY OF CYLINDRICAL WITH RESPECT TO SAID WORKPIECE, A PLURALITY OF HOUSINGS, A PLURALITY OF DRIVING SHAFTS, EACH OF WHICH IS ECCENTRICALLY MOUNTED IN ONE OF SAID HOUSINGS AND CARRIES AN ECCENTRIC IN DRIVING CONNECTION WITH ONE OF SAID HAMMERS TO MOVE IT RADIALLY INWARDLY WITH RESPECT TO SAID WORKPIECE, WHEREBY A ROTATION OF EACH OF SAID HOUSINGS IN ONE DIRECTION WILL CAUSE A RADIALLY OUTWARD SETTING MOVEMENT AND A ROTATION IN THE OPPOSITE DIRECTION WILL CAUSE A RADIALLY INWARD SETTING MOVEMENT OF ONE OF SAID HAMMERS, SAID MACHINE FURTHER COMPRISING A PLURALITY OF HYDRAULIC CYLINDERS, EACH OF WHICH CONTAINS A BACKING PISTON SLIDABLE IN SAID CYLINDER AND CONNECTED TO ONE OF SAID ADJUSTING HOUSINGS, CONDUIT MEANS, A SOURCE OF HYDRAULIC PRESSURE CONNECTED BY SAID CONDUIT MEANS TO SAID HYDRAULIC CYLINDERS TO OPPOSE A MOVEMENT OF SAID PISTON IN A DIRECTION CORRESPONDING TO A ROTATION OF SAID HOUSING IN SAID ONE DIRECTION, AND OVERPRESSURE RELIEF VALVE MEANS CONNECTED TO SAID HYDRAULIC CYLINDERS AND ARRANGED TO OPEN AND RELIEVE PRESSURE FROM SAID CYLINDERS IN A RESPONSE TO A PRESSURE IN SAID CONDUIT MEANS EXCEEDING A PREDETERMINED VALUE. 